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Journal of Thermal Science 2022年第6期31卷 2171-2177页

作者： KHAN Taj Wali qamar Ihtzaz Department of Aeronautics and Astronautics Institute of Space TechnologyIslamabad 44000Pakistan

Design, development, and testing of LPRE(Liquid Propellant Rocket Engine) are difficult and expensive tasks. Prior to full-scale design, it is indispensable to optimize important parameters at sub-scale. Propellants flow rates are low for a sub-scale or laboratory scale combustion chambers. It is hard to satisfy chamber cooling and chill feed lines quickly with low flow rates of propellants. This paper proposes a detailed procedure for testing of a laboratory scale semi-cryogenic combustion chamber. Many tests were conducted with a small scale adjustable length combustion chamber. The injection head of the chamber was interchangeable. Liquid-liquid pressure swirl injector and like impinging injectors were used with two different injection heads. Liquid oxygen and kerosene were used as oxidizer and fuel, respectively. Oxidizer to fuel mixing ratio was 0.29-0.45 and the total propellant mass flow rate was 0.06-0.1 kg/s. Problems were faced during testing, including, explosion in the combustion chamber, fuel injector blockage, unstable combustion, incomplete chilling and blockage of cooling water channel, etc. A detailed procedure is designed on the basis of the lessons learned which was experimentally proved.

关键词： LPRE cryogenic testing procedure combustion chamber

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Qualitative behavior of a discrete SIR epidemic model

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International Journal of Biomathematics 2016年第6期9卷 225-239页

作者： qamar Din Department of MathematicsThe University of Poonch Rawalakot Rawalakot 12350 Pakistan

In this paper, we study the qualitative behavior of a discrete-time epidemic model. More precisely, we investigate equilibrium points, asymptotic stability of both disease^free equilibrium and the endemic equilibrium. Furthermore, by using comparison method, we obtain the global stability of these equilibrium points under certain parametric con- ditions. Some illustrative examples are provided to support our theoretical discussion.

关键词： Discrete epidemic model steady-states local asymptotic stability globalbehavior.

Deep Convolutional Neural Network Based Churn Prediction for Telecommunication Industry

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Computer Systems Science & Engineering 2022年第12期43卷 1255-1270页

作者： Nasebah Almufadi Ali Mustafa qamar Department of Computer Science College of ComputerQassim UniversityBuraydahSaudi Arabia Department of Computing School of Electrical Engineering and Computer ScienceNational University of Sciences and Technology(NUST)IslamabadPakistan

Currently,mobile communication is one of the widely used means of ***,it is quite challenging for a telecommunication company to attract new *** recent concept of mobile number portability has also aggravated the problem of customer *** need to identify beforehand the customers,who could potentially churn out to the *** the telecommunication industry,such identification could be done based on call detail *** research presents an extensive experimental study based on various deep learning models,such as the 1D convolutional neural network(CNN)model along with the recurrent neural network(RNN)and deep neural network(DNN)for churn *** use the mobile telephony churn prediction dataset obtained from ***,containing the data for around 100,000 individuals,out of which 86,000 are non-churners,whereas 14,000 are churned *** imbalanced data are handled using undersampling and *** accuracy for CNN,RNN,and DNN is 91%,93%,and 96%,***,DNN got 99%for ROC.

关键词： Deep learning machine learning churn prediction convolutional neural network recurrent neural network

Influence of the iodide/iodine redox system on the self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte

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Progress in Natural Science:Materials International 2015年第6期25卷 622-630页

作者： qamar abbas Fran?ois Béguin Institute of Chemistry and Technical Electrochemistry Poznan University of Technology

Self-discharge(SD) of AC/AC(AC ? activated carbon) electrochemical capacitors in aqueous solutions of lithium sulfate(Li2SO4) and lithium sulfate t iodide salts(Li2SO4tKI or Li2SO4tLi I) was investigated at 24 1C and 40 1C after cell potential hold at values from 1 V to 1.6 ***24 1C,the cells exhibit lower SD in Li2SO4tKI than in Li2SO4,owing to the redox activity of the 2I /I2 system which drives the positive AC electrode to operate in narrow potential range and display lower potential drop than in *** 401 C,the capacitors exhibit comparable and reduced SD both in Li2SO4tLi I and Li2SO4,whatever the holding cell ***-electrode cell experiments demonstrate that,at 40 1C,hydrogen chemisorption is thermodynamically unfavored under negative polarization,while the activity of the 2I /I2 redox system under positive polarization is only slightly *** a consequence,the AC/AC cells in Li2SO4 exhibit a typical electrical double-layer performance at 401 C,whereas they still behave as hybrid ones in Li2SO4tLi I,with twice higher capacitance than in ***(Ui-Ut) vs t1/2plots demonstrate that SD is essentially controlled by diffusion at 401 C,suggesting that it originates from bulkier hydrated ***,in the investigated temperature range,the AC/AC capacitors in Li2SO4tLi I demonstrate low self-discharge and high capacitance,while being able to operate up to 1.6 V.

关键词： Supercapacitors Activated carbon Self-discharge Salt aqueous electrolyte Iodide/iodine redox system Activation and diffusion controlled mechanisms

Schamel equation in an inhomogeneous magnetized sheared flow plasma with q-nonextensive trapped electrons

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Chinese Physics B 2018年第2期27卷 428-434页

作者： Shaukat Ali Shan qamar-ul-Haque Theoretical Physics Division (TPD) PINSTECH

An investigation is carried out for understanding the properties of ion–acoustic（IA） solitary waves in an inhomogeneous magnetized electron-ion plasma with field-aligned sheared flow under the impact of q-nonextensive trapped electrons. The Schamel equation and its stationary solution in the form of solitary waves are obtained for this inhomogeneous plasma. It is shown that the amplitude of IA solitary waves increases with higher trapping efficiency（β）, while the width remains almost the same. Further, it is found that the amplitude of the solitary waves decreases with enhanced normalized drift speed, shear flow parameter and the population of the energetic particles. The size of the nonlinear solitary structures is calculated to be a few hundred meters and it is pointed out that the present results are useful to understand the solar wind plasma.

关键词： sheared flow plasma density inhomogeniety electron trapping

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Propagation of Ion Solitary Pulses in Dense Astrophysical Electron-Positron-Ion Magnetoplasmas

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Plasma Science and Technology 2015年第12期17卷 1000-1005页

作者： ATA-UR-RAHMAN S.A.KHAN A.qamar Department of Physics Theoretical Plasma Physics GroupIslamia College Peshawar(A Public Sector University) National Centre for Physics QAU Campus Department of Physics University of Peshawar

In this paper,we theoretically investigate the existence and propagation of low amplitude nonlinear ion waves in a dense plasma under the influence of a strong magnetic *** plasma consists of ultra-relativistic and degenerate electrons and positrons and non-degenerate cold ***,the appearance of two distinct linear modes and their evolution is studied by deriving a dispersion equation with the aid of Fourier ***,the dynamics of low amplitude ion solitary structures is investigated via a Korteweg-de Vries equation derived by employing a reductive perturbation *** effects of various plasma parameters like positron concentration,strength of magnetic field,obliqueness of field,etc.,are discussed in *** the end,analytical results are supplemented through numerical analysis by using typical representative parameters consistent with degenerate and ultra-relativistic magnetoplasmas of astrophysical regimes.

关键词： degenerate relativistic perturbation solitary representative Electron appearance dense collective normalized

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Data-Driven Load Forecasting Using Machine Learning and Meteorological Data

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Computer Systems Science & Engineering 2023年第3期44卷 1973-1988页

作者： Aishah Alrashidi Ali Mustafa qamar Department of Computer Science College of ComputerQassim UniversityBuraydahSaudi Arabia

Electrical load forecasting is very crucial for electrical power systems’planning and *** electrical buildings’load demand and meteorological datasets may contain hidden patterns that are required to be investigated and studied to show their potential impact on load *** meteorological data are analyzed in this study through different data mining techniques aiming to predict the electrical load demand of a factory located in Riyadh,Saudi *** factory load and meteorological data used in this study are recorded hourly between 2016 and *** data are provided by King Abdullah City for Atomic and Renewable Energy and Saudi Electricity Company at a site located in *** applying the data pre-processing techniques to prepare the data,different machine learning algorithms,namely Artificial Neural Network and Support Vector Regression(SVR),are applied and compared to predict the factory *** addition,for the sake of selecting the optimal set of features,13 different combinations of features are investigated in this *** outcomes of this study emphasize selecting the optimal set of features as more features may add complexity to the learning ***,the SVR algorithm with six features provides the most accurate prediction values to predict the factory load.

关键词： Electricity load forecasting meteorological data machine learning feature selection modeling real-world problems predictive analytics

Under the influence of crowding effects:Stability,bifurcation and chaos control for a discrete-time predator-prey model

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International Journal of Biomathematics 2019年第4期12卷 185-213页

作者： Muhammad Aqib Abbasi qamar Din Department of Mathematics University of the Poonch Rawalakot Pakistan

The interaction between predators and preys exhibits more complicated behavior under the influence of crowding effects. By taking into account the crowding effects, the qualitative behavior of a prey-predator model is investigated. Particularly, we examine the boundedness as well as existence and uniqueness of positive steady-state and stability analysis of the unique positive steady-state. Moreover, it is also proved that the system undergoes Hopf bifurcation and flip bifurcation with the help of bifurcation theory. Moreover, a chaos control technique is proposed for controlling chaos under the influence of bifurcations. Finally, numerical simulations are provided to illustrate the theoretical results. These results of numerical simulations demonstrate chaotic long-term behavior over a broad range of parameters. The presence of chaotic behavior in the model is confirmed by computing maximum Lyapunov exponents.

关键词： Prey-predator model stability analysis boundedness flip bifurcation Hopfbifurcation chaos control

A Space-Time Conservative Method for Hyperbolic Systems with Stiff and Non Stiff Source Terms

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Communications in Computational Physics 2006年第3期1卷 449-478页

作者： Shamsul qamar Gerald Warnecke Institute for Analysis and Numerics Otto-von-Guericke UniversityPSF 4120D-39106 MagdeburgGermany

In this article we propose a higher-order space-time conservative method for hyperbolic systems with stiff and non stiff source terms as well as relaxation *** call the scheme a slope propagation(SP)*** is an extension of our scheme derived for homogeneous hyperbolic systems[1].In the present inhomogeneous systems the relaxation time may vary from order of one to a very small *** small values make the relaxation term stronger and highly *** such situations underresolved numerical schemes may produce spurious numerical ***,our present scheme has the capability to correctly capture the behavior of the physical phenomena with high order accuracy even if the initial layer and the small relaxation time are not numerically *** scheme treats the space and time in a unified *** flow variables and their slopes are the basic unknowns in the *** source term is treated by its volumetric integration over the space-time control volume and is a direct part of the overall space-time flux *** use two approaches for the slope calculations of the flow variables,the first one results directly from the flux balance over the control volumes,while in the second one we use a finite difference *** main features of the scheme are its simplicity,its Jacobian-free and Riemann solver-free recipe,as well as its efficiency and high of order *** particular we show that the scheme has a discrete analog of the continuous asymptotic *** have implemented our scheme for various test models available in the literature such as the Broadwell model,the extended thermodynamics equations,the shallow water equations,traffic flow and the Euler equations with heat *** numerical results validate the accuracy,versatility and robustness of the present scheme.

关键词： Hyperbolic systems with relaxation stiff systems space-time conservative and Jacobian-free method high order accuracy discontinuous solutions

“Liverscore”is predictive of both liver fi brosis and activity in chronic hepatitis C

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World Journal of Gastroenterology 2011年第41期17卷 4607-4613页

作者： Shoukat Ali Arain qamar Jamal Amir Omair Department of Pathology Ziauddin University4/BShara-e-GhalibBlock 6 Clifton College of Medicine Alfaisal University Department of Medical Education King Saud bin Abdulaziz University for Health Sciences

AIM:To formulate a noninvasive index predictive of se-verity of liver f ibrosis and activity in chronic hepatitis ***:This cross sectional study was conducted on polymerase chain reaction positive,treatment nave *** was staged on a f ive point scale from F0-F4 and activity was graded on a four point scale from A0-A3,according to the METAVIR *** were divided into two overall severity groups,minimal disease(< F2 and < A2)and signif icant disease(≥ F2 or ≥ A2).Eleven markers were measured in ***-tistically,the primary outcome variable was identif ica-tion of minimal and signif icant overall *** were formulated using β regression values of different combinations of nine statistically significant *** performance of these indices was assessed through receiver-operating characteristic curve ***:A total of 98 patients were included and of these 46 had an overall clinically significant *** f inal six marker index,Liverscore for Hepatitis C,consisted of age,alanine transaminase,gamma-gluta-myl transpeptidase,apolipoprotein A-1,alpha-2 macro-globulin and hyaluronic *** area under the curve was found to be *** a 0-1 scale,negative predic-tive value at a cutoff level of ≤ 0.40 was 83%,while positive predictive value at ≥ 0.80 remained 89%.Al-together,61% of the patients had these discriminative ***:This index is discriminative of minimal and significant overall liver disease in a majority of chronic hepatitis C patients and can help in clinical de-cision making.

关键词： Chronic hepatitis C Staging and grading Liver fibrosis and activity, Noninvasive assessment Liverscore